(a) of FIG. 7 is a plan view illustrating pixel auxiliary capacitor parts (thin film capacitor parts) and a peripheral circuit of a conventional liquid crystal display device. (b) of FIG. 7 is a cross-sectional view taken along line X-X of (a) of FIG. 7.
As illustrated in (a) and (b) of FIG. 7, a liquid crystal display device has conventionally employed a number of thin film elements as pixel auxiliary capacitor parts (thin film capacitor parts) 110, each of which film elements includes a lower electrode 101, an insulating layer 102, and an upper electrode 103, which are provided on a substrate.
Not only a liquid crystal display device, but also a data storage memory cell includes the thin film capacitor parts. For example, Patent Literature 1 discloses a dynamic random access memory including lower capacitor electrodes 151 (lower electrodes); an insulating layer (not illustrated); and upper capacitor electrodes 152 (upper electrodes), which are provided on a substrate (see FIG. 8).
Meanwhile, in a case where the thin film capacitor parts illustrated in (a) and (b) of FIG. 7, each of which includes the lower electrode 101, the insulating film 102, and the upper electrode 103, are provided in pixels adjacent to each other across a corresponding source metal wire in such a manner that they partly shares a same structure with each other, the thin film capacitor parts are configured such that in a case where upper electrodes 103 of each of the pixels are connected to each other with a wire serving as a layer of the electrodes 103, edge portions 101a of lower electrodes 101, which edge portions 101a are opposed to each other in a region where the corresponding source metal wire is provided, are covered with the insulating film 102 and the wire.
In such a configuration, there has been the following problem. The insulating layer 102 and the wire are stepped in the edge portions 101a of the lower electrodes 101. As a result, the insulating layer 102 cannot sufficiently cover the lower electrodes 101 in the stepped regions. This results in a decrease in voltage resistance, and thus causes an insulation breakdown in a capacitor part to which high voltage is applied. The insulation breakdown leads to a leakage between the upper electrodes 103 and the lower electrodes 101.
This problem is specifically disclosed also in, for example, Patent Literature 2. (a) to (h) of FIG. 9 show a conventional manufacturing process drawing disclosed in Patent Literature 2.
More specifically, Patent Literature 2 describes that a first-layer polysilicon gate electrode 201, which is vertically etched, and a second gate oxide film 202, which is provided on the first-layer polysilicon gate electrode 201 by thermal oxidation, tend to swell outwards (part B in (e) of FIG. 9), and the second gate oxide film 202 tends to be extremely thin in the vicinity (part B′ in (e) of FIG. 9) of a first gate oxide film 203 due to for example inner skewness caused by a thermal stress.
Patent Literature 2 further discloses the following problem. As illustrated in (f) of FIG. 9, a second-layer polysilicon film of approximately 3000 Å in thickness is formed on the second gate oxide films 202 and 202′ by an LPCVD method, and then phosphorus diffusion is performed, so that the second-layer polysilicon film turns into a second-layer polysilicon gate electrode 204. Here, an edge portion of the second-layer polysilicon gate electrode 204 is overhanged (part C in (f) of FIG. 9) due to effects of a swelled part (part B) and a thin part (part B′) shown in (f) of FIG. 9. This makes it difficult to ensure a sufficient voltage resistance between the first-layer polysilicon gate electrode 201 and the second-layer polysilicon gate electrode 204 in part B and part B′ of FIG. 9, and as a result, a voltage breakdown occurs. The voltage breakdown leads to a leakage between the first-layer polysilicon gate electrode 201 and the second-layer polysilicon gate electrode 204.
In order to solve the problem, Patent Literature 2 discloses an arrangement in which an edge portion of the first-layer polysilicon gate electrode 201 is etched so that the edge portion tapers off (see (a) to (h) of FIG. 10). With the arrangement, the second gate oxide film 202 has a smooth surface with no overhang. As a result, the second gate oxide film 202 sufficiently covers the first-layer polysilicon gate electrode 201, thereby ensuring a sufficient voltage resistance between the first-layer polysilicon gate electrode 201 and the second-layer polysilicon gate electrode 204.
Patent Literature 3 discloses a liquid crystal display element in which auxiliary capacitor wires are provided all over a liquid crystal display device in a mesh manner so as to reduce an adverse effect associated with disconnection of the auxiliary capacitor wires.
Patent Literature 4 discloses a configuration in which gate lines and auxiliary capacitor lines are arranged such that (i) the gate lines and the auxiliary capacitor lines each have a two-layer structure made of Cr and ITO in a region other than a region where the gate lines and the auxiliary capacitor lines intersect with, not in a same layer (cross over), lines provided around each display region and (ii) the ITO lines are exposed in contact holes.
Patent Literature 5 discloses a configuration in which horizontal signal lines and vertical signal lines are intersecting with each other in such a manner that each of the horizontal signal lines continuously extends whereas each of the vertical signal lines breaks at a corresponding intersection of the horizontal signal lines and, the vertical signal lines, and vertical signal lines thus broken are connected to each other with another wire layer provided in a layer positioned above the corresponding intersection of the horizontal signal lines and vertical signal lines. With the configuration, disconnection of the vertical signal lines and of the horizontal signal lines is prevented, thereby enhancing reliability of signal lines.
Citation List
Patent Literature 1
Japanese Patent Application Publication, Tokukaihei, No. 4-274359 A (Publication Date: Sep. 30, 1992)
Patent Literature 2
Japanese Patent Application Publication, Tokukaisho, No. 61-264740 A (Publication Date: Nov. 22, 1986)
Patent Literature 3
Japanese Patent Application Publication, Tokukaihei, No. 9-160075 A (Publication Date: Jun. 20, 1997)
Patent Literature 4
Japanese Patent Application Publication, Tokukaihei, No. 5-323375 A (Publication Date: Dec. 7, 1993)
Patent Literature 5
Japanese Patent Application Publication, Tokukai, No. 2003-110019 A (Publication Date: Apr. 11, 2003)